The present invention relates to a variable displacement swash plate compressor.
Japanese Laid-Out Patent Publication Nos. 5-172052 and 52-131204 describe conventional variable displacement swash plate compressors (hereafter simply referred to as the compressors). The compressors each have a housing including a suction chamber, a discharge chamber, a swash plate chamber, and a plurality of cylinder bores. A rotatable drive shaft is supported in the housing. A swash plate that is rotatable together with the drive shaft is arranged in the swash plate chamber. A link mechanism is located between the drive shaft and the swash plate to allow the inclination angle of the swash plate to change. The inclination angle refers to an angle relative to a direction orthogonal to the rotation axis of the drive shaft. Each cylinder bore accommodates a piston. The piston reciprocates in the cylinder bore and defines a compression chamber in the cylinder bore. A conversion mechanism coverts rotation of the swash plate to reciprocation of the piston in each cylinder bore. The stroke when the piston reciprocates is in accordance with the inclination angle of the swash plate. The inclination angle of the swash plate is changed by an actuator, which is controlled by a control mechanism.
In the compressor described in Japanese Laid-Out Patent Publication No. 5-172052, each cylinder bore pair, which is formed in a cylinder block of the housing, includes a first cylinder bore, which is located at the front side of the swash plate, and a second cylinder bore, which is located at the rear side of the swash plate. Each piston includes a first head, which reciprocates in the corresponding first cylinder bore, and a second head, which reciprocates in the corresponding second cylinder bore.
The compressor includes a pressure regulation chamber in a rear housing member, which forms the housing with the cylinder block. In addition to the cylinder bore pairs, the cylinder block includes a control pressure chamber that is in communication with the pressure regulation chamber. The control pressure chamber is located at the same side as the second cylinder bores, that is, the rear side of the swash plate. The actuator is located in a control pressure chamber. The actuator is not rotated integrally with the drive shaft. More specifically, the actuator includes a non-rotation movable body that covers the rear end of the drive shaft. The non-rotation movable body includes an inner wall surface that supports the rear end of the drive shaft so that the rear end is rotatable. The non-rotation movable body is movable along the rotation axis of the drive shaft. Although the non-rotation movable body moves in the control pressure chamber along the rotation axis of the drive shaft, the non-rotation movable body is not allowed to rotate about the rotation axis of the drive shaft. A spring that urges the non-rotation movable body toward the front is arranged in the control pressure chamber. The actuator includes a movable body, which is coupled to the swash plate and movable along the rotation axis of the drive shaft. A thrust bearing is arranged between the non-rotation movable body and the movable body. A pressure control valve, which changes the pressure of the control pressure chamber, is arranged between the pressure regulation chamber and the discharge chamber. A change in the pressure of the control pressure chamber moves the non-rotation movable body and the movable body in the axial direction of the drive shaft.
A link mechanism includes a movable body and a lug arm, which is fixed to the drive shaft and located at the front side of the swash plate. The movable body includes a first elongated hole, which extends in a direction orthogonal to the rotation axis of the drive shaft and in a direction from a radially outer side toward the rotation axis of the drive shaft. The lug arm includes a second elongated hole, which extends in a direction orthogonal to the rotation axis of the drive shaft and in a direction from a radially outer side toward the rotation axis of the drive shaft. The swash plate includes a first arm, which is located on the rear side and which extends toward the second cylinder bores, and a second arm, which is located on the front side and which extends toward the first cylinder bores. A first pin is inserted to the first elongated hole. Thus, the first arm is supported by the movable body pivotally about the first pin. This couples the swash plate to the movable body. A second pin is inserted to the second elongated hole. Thus, the second arm is supported by the lug arm pivotally about the second pin. This couples the swash plate to the lug arm. The first pin extends parallel to the second pin. The first and second pins are inserted to the first and second elongated holes so that the first and second pins are located at opposite sides of the drive shaft in the swash plate chamber.
In this compressor, the pressure control valve opens to connect the discharge chamber and the pressure regulation chamber so that the pressure of the control pressure chamber becomes higher than that of the swash plate chamber. This moves the non-rotation movable body and the movable body toward the front. Thus, the movable body pushes the swash plate while pivoting the first arm of the swash plate about the first pin. Simultaneously, the lug arm pivots the second arm of the swash plate about the second pin. In this manner, the movable body uses the first pin as an action point and the second pin as a fulcrum point to pivot the swash plate. In this manner, the inclination angle of the swash plate increases in the compressor, the piston stroke is lengthened. This increases the compression displacement for each rotation of the drive shaft.
When the pressure control valve closes to disconnect the discharge chamber and the pressure regulation chamber, the pressure of the control pressure chamber becomes low and about the same as that of the swash plate chamber. This moves the non-rotation movable body and the movable body toward the rear, which is the direction opposite to when increasing the inclination angle of the swash plate. Thus, the movable body pulls the swash plate while pivoting the first arm of the swash plate about the first pin. Simultaneously, the lug arm pivots the second arm of the swash plate about the second pin. Consequently, the inclination angle of the swash plate decreases and the piston stroke is shortened. This decreases the compressor displacement for each rotation of the drive shaft.
In the compressor of Japanese Laid-Open Patent Publication No. 52-131204, the actuator is rotatable integrally with the drive shaft in the swash plate chamber. More specifically, the actuator includes a partitioning body fixed to the drive shaft. The partitioning body accommodates a movable body, which is movable relative to the partitioning body along the rotation axis. A control pressure chamber is defined between the partitioning body and the movable body to move the movable body with the pressure of the control pressure chamber. A communication passage, which is in communication with the control pressure chamber, extends through the drive shaft. A pressure control valve is arranged between the communication passage and the discharge chamber. The pressure control valve is configured to change the pressure of the control pressure chamber and move the movable body relative to the partitioning body along the rotation axis. The movable body includes a rear end that is in contact with a hinge ball. The hinge ball pivotally couples the swash plate to the drive shaft. A spring, which urges the hinge ball in the direction that increases the inclination angle of the swash plate, is arranged at the rear end of the hinge ball.
A link mechanism includes the hinge ball and an arm, which is located between the partitioning body and the swash plate. The spring urges the hinge ball from the rear and holds the hinge ball in contact with the partitioning body. A first pin, which extends in a direction orthogonal to the rotation axis, is inserted to the front end of the arm. A second pin, which extends in a direction orthogonal to the rotation axis, is inserted to the rear end of the arm. The swash plate is pivotally supported by the arm and the first and second pins.
In this compressor, a pressure regulation valve opens to connect the discharge chamber and the pressure regulation chamber so that the pressure of the control pressure chamber becomes higher than that of the swash plate chamber. This moves the movable body toward the rear and pushes the hinge ball against the urging force of the spring. Accordingly, the arm pivots about the first and second pins. Thus, the swash plate pivots using the first pin as a fulcrum point and the second pin as an action point. Consequently, the inclination angle of the swash plate decreases and shortens the stroke of the pistons. This decreases the compressor displacement for each rotation of the drive shaft.
When the pressure regulation valve closes and disconnects the discharge chamber and the pressure regulation chamber, the pressure of the control pressure chamber becomes low and about the same as the swash plate chamber. This moves the movable body toward the front, and the hinge ball follows the movable body due to the urging force of the spring. Thus, the swash plate pivots in a direction opposite to when the inclination angle of the swash plate is decreased. This increases the inclination angle of the swash plate and lengthens the stroke of the pistons.
A variable displacement swash plate compressor using an actuator such as that described above needs to be accurately controlled.
The compressors of Japanese Laid-Open Patent Publication Nos. 5-172052 and 52-131204 each increase the pressure of the control pressure chamber so that the movable body, which is one component of the actuator, pushes the swash plate when changing the inclination angle of the swash plate. Thus, when enlarging the movable body in the radial direction to increase the pushing force applied to the swash plate, the movable body will interfere with the swash plate when the inclination angle of the swash plate increases as the movable body moves in the pushing direction. This makes it difficult to arrange the actuator in the swash plate chamber. To avoid interference like that described above, the movable body would need to have a complicated form. This would enlarge the compressor and adversely affect the degree of layout freedom when installing the compressor in a vehicle or the like.
In the compressor of Japanese Laid-Open Patent Publication No. 5-172052, when increasing the inclination angle of the swash plate, the movable body needs to push the swash plate against the compression reaction and suction reaction, which have a tendency of increasing. This may deform the movable body when the movable body has a complicated form. The weight of the movable body is increased to increase the rigidity of the movable body and avoid deformation. However, this would increase the weight of the compressor and raise the manufacturing cost of the compressor.